In the conversion of radiated energy to electrical energy, it has been the practice in the art to use solid state semiconductor layer structures that can produce hole-electron pairs that result from atomic particles or photons, in passing through the semiconductor, engaging in primary or secondary collisions with the semiconductor material. The oppositely charged hole-electron pairs are extracted from the absorber and into external circuitry as a signal before they can recombine or be trapped in the semiconductor material.
The environment in which the conversion device is to be used also has a major influence in the design. Use in the atmosphere, nominally Air Mass 1.5 (AM1.5), usually takes place at room temperature in light with a moderate ultra violet (UV) content and minimal other energy radiation. Structural weight is of less concern. Use beyond the atmosphere, in Air Mass 0 (AM0), involves a larger range of temperatures, structural weight is a serious consideration, the radiated energy, usually sunlight is intense with a larger UV content and operation is often in the presence of significant external energy radiation. Structures for AM0 operation frequently have features designed to "harden" or slow down deteriorating effects of external radiation on the performance of the conversion device.
The single absorption layer type of radiated energy to electrical energy conversion device has the advantages of essentially unlimited breadth of device area and relative simplicity in structural features and in fabrication. There are however, in such a device, interrelated structural features that both produce and extract the electrical energy together with reflective mechanisms that operate to get more than one pass out of the radiated energy in hole-electron pair production that, heretofore in the art, required tradeoffs that had a limiting effect on efficiency and made control of radiation damage more difficult.
Among the influencing factors in the design of single absorption member radiated energy to electrical energy conversion structures are: the absorption lengths of the incident radiated energy in the semiconductor material, the compatibility of any radiated energy enhancement features with the extraction of the electrical energy, the attenuation of the radiated energy by the contacting structure and the compatibility of the overall conversion device structure with manufacturing capability.
There has been activity in the art directed to single absorption member semiconductor radiated energy to electrical energy converters. In U.S. Pat. Nos. 5,286,306; 5,342,455; 5,401,330; and 5,419,783 conversion devices are described wherein structural features that are placed in the absorber region of the absorption member for one purpose, interfere with or add complexity, with respect to another purpose. There is a need in the single absorption member art for a radiation conversion device that can provide high efficiency achieved with structural and manufacturing simplicity.